Heretofore, a pipe expanding apparatus of the above type is arranged as shown in FIG. 5, for example. A frame 9a is uprightly provided on a base 9 and a cylinder 10 is mounted at the top of the frame 9a, with a plurality of mandrels 12 vertically downwardly extending from a reciprocating member 11. The reciprocating member 11 is vertically movable upon extension and contraction of the cylinder 10, and is installed in place with the aid of plural guide posts 13 for guiding the vertical movement of the reciprocating member 11 in slidable relation. Pipes 14 to be expanded are previously set at positions corresponding to the mandrels 12 attached to the reciprocating member 11. When the reciprocating member 11 is descended, the mandrels 12 are inserted into the corresponding pipes 14 under pressure for thereby expanding the pipes arranged in a desired pattern.
However, the conventional pipe expanding apparatus described above has suffered from the problems as follows.
In the above conventional pipe expanding apparatus, the pipes to be expanded, the mandrels for expanding the pipes, the reciprocating member, and the cylinder for vertically moving the reciprocating member are all provided to line up successively in the longitudinal direction of the pipe expanding apparatus. This makes the entire length of the pipe expanding apparatus very large in the direction of expanding the pipes.
Accordingly, in the case the above pipe expanding apparatus is of the vertical type, for example, the entire height of the apparatus is extremely increased, which makes it very difficult to carry and install the apparatus in buildings such as factories.
Further, the conventional pipe expanding apparatus has the guide posts provided to slidably penetrate through four corners of the reciprocating member for vertically moving the reciprocating member in a smooth manner when the pipes are expanded, without causing any distortion such as a twist. In addition, the cylinder is disposed between the laterally spaced pairs of the guide posts, and has a rod 10a which is extended and contracted to respectively descend and ascend the reciprocating member.
With such arrangement, the cylinder for vertically moving the reciprocating member must be given by a single cylinder of large capacity located substantially at the center of the reciprocating member in consideration of the problem of space. Such a large-capacity cylinder has the very high cost per unit. Moreover, the guide posts disposed at both lateral side ends of the reciprocating member are generally employed four in number to penetrate through its four corners, respectively, for smooth vertical movement of the reciprocating member upon extension and contraction of the cylinder located substantially at the center of the reciprocating member. This requires the cost of the four guide posts.